Re: [RFC PATCH v2 1/3] vfio: Move the saving of the config space to the right place in VFIO migration

[Cornelia Huck]

On Wed, 9 Dec 2020 16:09:17 +0800
Shenming Lu <lushenming@huawei.com> wrote:

> On ARM64 the VFIO SET_IRQS ioctl is dependent on the VM interrupt
> setup, if the restoring of the VFIO PCI device config space is
> before the VGIC, an error might occur in the kernel.
> 
> So we move the saving of the config space to the non-iterable
> process, so that it will be called after the VGIC according to
> their priorities.
> 
> As for the possible dependence of the device specific migration
> data on it's config space, we can let the vendor driver to
> include any config info it needs in its own data stream.
> (Should we note this in the header file linux-headers/linux/vfio.h?)

Given that the header is our primary source about how this interface
should act, we need to properly document expectations about what will
be saved/restored when there (well, in the source file in the kernel.)
That goes in both directions: what a userspace must implement, and what
a vendor driver can rely on.

[Related, but not a todo for you: I think we're still missing proper
documentation of the whole migration feature.]

> 
> Signed-off-by: Shenming Lu <lushenming@huawei.com>
> ---
>  hw/vfio/migration.c | 25 +++++++++++++++----------
>  1 file changed, 15 insertions(+), 10 deletions(-)